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Shimano One Key Crank Bolt Torque

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Shimano One Key Crank Bolt Torque

Old 09-21-17, 04:06 PM
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Shrevvy 
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Shimano One Key Crank Bolt Torque

What is the correct torque for the Shimano 600 Arabesque crank bolts with one key release? I have seen a chart that shows 5-6.8 nm or 44-60 in lbs. Most of the other crank bolt torque specs are 5x that amount. Is the one key release really that much less torque?


Torque Specifications - Bicycle Tutor
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Old 09-21-17, 05:00 PM
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That sounds like the torque for installing the one key bolt/tool into the crank arm, not the crank itself. I'm reasonably sure the required crank bolt torque to fix the crank is the same as a typical square taper crank.

I vaguely remember taking those things out, using regular bolt to fix the crank, and then reinstalling the one key release.
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Old 09-21-17, 06:35 PM
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-----

Since this is the C & V forum many readers will be aware that an earlier one key release mechanism was found on the Magistroni Super Zenith chainset of 1965.



The tool in the upper right corner is for the "dustcap" against which the fixing bolt's shoulder pushes to achieve removal.

-----
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Old 09-21-17, 07:41 PM
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That would make more sense. Thanks.
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Old 09-22-17, 06:43 AM
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While I'm sure they will work (at least once...), I had a pair of one-key crank bolts, and had the caps almost immediately begin buckling when I went to remove the crank. Maybe they were knockoffs?

At any rate, I bought a pair of the White Industries bolts, which have the extractor ring made out of bronze. A tiny bit heavier, but rock solid (and maybe not C&V, but...)
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Old 09-22-17, 09:43 AM
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I first encountered Shimano's one-key 600 cranks on an inexpensive Ross back in 1981 or so, and from the beginning I felt that their system was under-built, especially the 6mm hex key recess in the bolt. Thirty foot-pounds seemed like too much for such a thin wrench!


I figured out that in order to effect more press-fit (or more extraction pull) using the 6mm wrench, that torqueing the bolt either way twice (with some jumping on the pedals in between efforts) would sufficiently twist the square taper in it's bore to allow greater movement for any level of torque applied to the wrench.


To this day, whenever I find a crankarm difficult to remove, I leave the puller fully tightened in place and jump on the pedals with the crankarms horizontal, one way then the other, re-torqueing the tool after each effort. This gets even a stubborn crankarm moving off of the spindle. And likewise, as when torqueing alloy crankarm bolts, bolts with 6mm hex recess or especially those nasty, coarse-threaded nutted spindles, I am still able to get the arms quite reliably seated on the spindle tapers by jumping on the pedals between modest tightening efforts.
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Old 09-22-17, 10:43 AM
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Roughly a billion years ago when I worked as "Saturday Boy" in my local cycle shop, we used to shut the door to the public, lift bikes horizontally with the crank arms rested on a softwood plate and bash the cranks onto the bottom bracket axle with a soft-faced hammer before tightening the bolts (or nuts for some SR cranks). The logic explained to me was that the taper is supposed to be a press fit and the bolt merely to stop in moving rather than the bolt ever being intended to press the crank onto the axle.

Whilst if doing this today I would be much happier using a press than a hammer, I can still see the sense in it and am uncomfortable leaning on a bog-standard long spanner to drive the crank on to the axle.

Z
PS/ I think we put a thin layer of grease on there too. Never had any issues removing a crank.

Last edited by ZG862; 09-25-17 at 01:49 AM. Reason: Left out "-standard" for some reason. Senior moment.
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Old 09-22-17, 11:28 AM
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The fine-threaded, steel, 8mm bolt with ~30 ft-lbs applied is a near-perfect way to apply the correct full press-fit force.


By comparison, the threaded studs of nutted spindles use an inferior metallurgy to bolts, and with a 10mm diameter, coarser thread which is far less effective at translating wrench torque into pressing force. So they add teeth to the nut's built-on washer surface to help prevent loosening. I've found the nutted spindle threads prone to cracking off if the too-shallow nut is tightened as tightly as it should be if secured in one go. So I instead, prefer to apply a second round of torqueing after loading the assembly across the pedals with force.


I suspect that many rider/mechanics would be surprised by just how tight that 30 ft-lbs is, when applied with ordinary hand tools such as an 8mm hex key or crank bolt wrench, but that is what is called for and the steel bolts can take it. I've seen a lot of crankarms come loose and suspect they were never fully torqued to the specified range.


Impact isn't a bad method for securing press-fits, since the impact can effectively deliver the peak force needed to overcome friction without needing enough total energy to perhaps over-press an arm onto a taper. But I have to wonder how wide of a range of values can result from the random blows of a hammer when for instance the impact surfaces might be randomly canted a few degrees this way or that. A press adds a degree of control to the force level, ...and the bolt is a near-perfect press.


I've rarely used a torque wrench on any kind of crank bolt, but find myself subtly adjusting the wrench force used on the particular cranks that I am working on.

Last edited by dddd; 09-22-17 at 11:32 AM.
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Old 09-25-17, 01:56 AM
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Originally Posted by dddd View Post
Impact isn't a bad method for securing press-fits, since the impact can effectively deliver the peak force needed to overcome friction without needing enough total energy to perhaps over-press an arm onto a taper. But I have to wonder how wide of a range of values can result from the random blows of a hammer...
Please take that back sir. I'll have you know these trained craftsmen could deliver the same blow to within +-0.00638 N time after time. And their ear canals were so finely tuned to the gravitational centre of the earth that no crank was ever presented to the hammer face a more that 4 seconds of a degree out of true. Fact.

Or maybe that's a load of tosh and I fully accept your well-made counter argument.

Z
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Old 09-25-17, 10:49 AM
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Seriously, I've learned to never underestimate a craftsman!
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